ARCNET(Attached Resource Computer NETwork ) is a widely-installed local area network (LAN) technology that was introduced by Datapoint Corporation in 1977. ARCNET is one of the 4 main LAN technologies(the other three are Ethernet, Token Ring and FDDI) which uses a fieldbus scheme for managing line sharing among the workstations and other devices connected on the LAN. In addition, a special advantage of ARCNET is that it permits various types of transmission media, such as twisted-pair wire, coaxial cable, and fiber optic cable etc. to be mixed on the same network. ARCNET became popular in the 1980s for office automation tasks. It was later applied to embedded systems where certain features of the protocol are especially useful. Untill now, it still plays an important role in network structure.
ARCNET is an ideal fieldbus. In ARCNET, the LAN server continuously circulates empty message frames on a bus (a line in which every message goes through every device on the line and a device uses only those with its address). When a device wants to send a message, it inserts a “token” (this can be as simple as setting a token bit to 1) in an empty frame in which it also inserts the message. When the destination device or LAN server reads the message, it resets the token to 0 so that the frame can be reused by any other device. As a result, it becomes more efficient when traffic increases since all devices are afforded the same opportunity to use the shared network.